In Band On Channel (IBOC) system is a broadcast system capable of simultaneously implementing an analog broadcast and a digital broadcast by using the existing AM/FM frequency bands. This system was authorized by the Federal Communication Commission (FCC) in 2002, and has been recently increasingly spreading as the HD radio broadcast.
In a receiving device for Radio Data System (RDS) or Broadcast Data System (BDS) which are FM multiplex broadcast systems, an Alternative Frequency (AF) check is adopted. The AF check is an operation for examining reception qualities of alternative frequencies in order to find broadcast stations broadcasting identical contents in a better reception quality than that of the current received station when the reception status of the current received station deteriorates. When the alternative frequency has the better reception quality, the alternative frequency is continuously received. When the alternative frequency has worse reception quality, the original frequency is received.
Patent Literature 1 discloses an example of a conventional receiving device for receiving a broadcast wave in the IBOC system. This device includes a diversity receiving unit to control a diversity switching part to be in an enabled state and to select an output of a narrow-band filter when determining that the received broadcast wave does not include IBOC broadcast wave. On the other hand, when the diversity receiving unit determines that the received broadcast wave includes IBOC broadcast wave, the diversity switching part is controlled to be in a disenabled state and to select an output of a wide-band filter. According to those controls, the reception status of IBOC broadcast and the analog broadcast are optimized.
The conventional receiving device typified by Patent Literature 1, however, has a problem in that, if an alternative frequency is received even for a short time by performing AF check during reception of a digital broadcast, a “synchronization loss” may occur at a timing when acquiring digital data while the alternative frequency is switched to the current received station that has received the digital broadcast. This situation sometimes causes deterioration of the performance of receiving the digital broadcast.
The present invention is made to solve the problem mentioned above, and an object thereof is to acquire a receiving device capable of preventing a reception of digital broadcast from a synchronization loss caused by AF check.